In high-intensity white LED devices whose application to generic illumination has been studied, the use of encapsulation materials having excellent light transmitting property, light resistance and heat resistance has been studied, rather than epoxy resins which have been widely used in conventional display LED devices. As such encapsulation materials, attention has been attracted to thermosetting silicone resins and modified materials thereof.
JP-A-2000-198930 discloses a resin composition excellent in light transmitting property and insulating characteristics, which is obtained by introducing an organopolysiloxane having a resin structure into an addition curing type silicone composition utilizing a hydrosilylation reaction to set the molar ratio of silicon-bonded hydrogen atoms/silicon-bonded alkenyl groups in the composition to a specific range.
JP-A-2004-126168 reports that an addition curing type silicone resin composition containing a silicone resin having at least two silicon atom-bonded alkenyl groups in one molecule thereof, an organohydrogensilane and/or an organohydrogenpolysiloxane having at least two silicon atom-bonded hydrogen atoms in one molecule thereof and an addition reaction catalyst as essential components provides a transparent cured material excellent in light transmitting property and discoloration resistance.
JP-A-2008-150437 reports that a cured material giving an excellent strength is obtained by using a straight-chain polyorganohydrogensiloxane having a silicon atom-bonded hydrogen atom (a Si—H group) midway of a molecular chain and a straight-chain polyorganohydrogensiloxane having a silicon atom-bonded hydrogen atoms (Si—H groups) at both ends of a molecular chain in specific amounts, in a photosemiconductor encapsulation silicone rubber composition containing a polyorganosiloxane having 0.2 or more silicon atom-bonded alkenyl group on average in one molecule thereof.